Research for Pathophysiology of Cancer Related Fatigue (CRF) and Chronic Fatigue Syndrome (CFS/ME) by Lipidomics, Metabolomics, Intestinal and Peritoneal Microbiome Analysis and Exome Analysis and Investigation of a Possible Benefit of Probiotics.

This study aims to identify the underlying pathophysiology of Cancer Related Fatigue (CRF) by screening lipidome, metabolome, exome and microbiome of affected patients with tumor disease with and without fatigue. These results will be compared to an age- and gender matched control group with a comparable tumor disease and to another age- and gender matched control group without tumor disease.

The investigators are following the same strategy for investigating an underlying pathophysiology of Chronic Fatigue Syndrome (CFS/ME) in another group of patients. The age- and gender matched control group will be established from the beforementioned control group.

The investigators will also be screening for a peritoneal microbiome (possible correlate for leaky gut) in study patients undergoing abdominal surgery.

We will also investigate changes in fatigue and in lipidome, metabolome, exome and microbiome by double-blinded, placebo-controlled administration of probiotics to the study population.

Inclusion Criteria:

• histologically, cytologically or radiologically confirmed tumor disease
• indication for chemotherapy
• Written consent to participation

Exclusion Criteria:

• chronic-inflammatory bowel disease
• pregnancy

Blinding will be made at the probiotics manufacturer's establishment. Neither investigators nor care providers nor patients know their status til the end of the study.